1. Field of the Invention
The present invention relates to a method and apparatus for connecting a branch pipe to a main pipe. More specifically, this invention relates to tapping a branch pipe into a main, double-walled or ribbed reinforced sewer pipe and sealing the connection between the pipes by utilizing a tubular gasket therebetween. The tubular gasket not only seals between the two pipes, but also seals the space between the two walls of the double-walled pipe.
2. Description of the Prior Art
It is known to employ plastic pipes and fittings in the design and construction of underground conduit systems for conveyance of water and drainage purposes. In the past, such plastic pipes have been extruded into various lengths and diameters depending upon their use. However, extrusion of plastic pipes, such as PVC (polyvinyl chloride) pipes, have been limited in the past by diameter and weight, thus preventing competition with conventional concrete pipes for large-diameter sewer applications.
However, relatively recent advances in technology have enabled production of heavy-duty PVC pipes with bores up to 60 inches in diameter and larger, which is large enough to compete with concrete pipes. For example, systems for producing large-diameter, hollow profile pipes are described in U.S. Pat. Nos. 3,917,500 to Petzetakis and 4,033,808 to Petzetakis involving spiral winding and infrared welding of an extruded, hollow, core profile pipe.
While this hollow form of pipe has many advantages including production of heavy-duty PVC pipe with very large bores, it also has some disadvantages. A particular problem encountered with this form of pipe is the extruded, hollow core profile produces spiral and helical channels in which internal fluid can leak into, and then exit out the end of the pipe via the channels. This problem is enhanced by tapping a branch pipe into the side wall of the double-walled pipe.
In particular, when tapping a branch pipe into the side wall of a double-walled pipe, a plurality of helical or spiral channels will be intersected upon cutting the aperture into the side wall of the main pipe for receiving the branch pipe therein. This creates the problem of fluid leaking into the channels. Thus, not only must a seal between the two pipe be provided, but also each of the channels has to be sealed to prevent fluid from leaking into the channels.
The most popular type of sewer tapping system is a saddle tap. Examples of sewer saddle taps are disclosed in U.S. Pat. Nos. 3,663,042 to Fowler; 4,494,780 to Burnett; and 4,966,397 to McKinnon, which are all hereby incorporated herein by reference. Although, these saddle taps perform quite well on single walled pipe, they do not perform as well on double-walled pipe. In particular, a saddle tap does not provide any sealing of the channels intersecting with the aperture in the double-walled pipe. Moreover, saddle taps are difficult to install on existing pipe in the ground since an entire section of the pipe must be uncovered to attach the straps of the saddle tap around the main pipe.
Numerous other pipe connection assemblies or sewer taps are known in the prior art. However, none of these prior pipe connection assemblies or sewer taps recognize or address the problem of fluid leaking into the channels of a double-walled pipe. Moreover, many of these prior pipe connection assemblies are difficult to install and expensive to manufacture. For example, U.S. Pat. No. 4,365,829 to Fowler discloses a sewer tapping apparatus for connecting a branch pipe to a single walled main pipe composed of concrete.
Examples of other pipe connection assemblies are Mitchell; 3,677,578 to Roos; 3,819,118 to Brock et al; 3,863,960 to Anderson; 3,879,069 to Oostenbrink; 3,958,313 to Rossborough; 3,953,555 to Gley; 4,009,545 to Rossborough; 4,155,572 to Bertone, Jr.; 4,232,421 to Tucker; 4,550,451 to Hubbard; 4,706,999 to Hynes; and 4,905,940 to Luka.